1. Field of the Invention
The present invention relates to electrical contacts and more particularly to a one-piece semi-rigid electrical contact with an integral compression spring for use in solderless high-speed electrical connectors, that is, electrical connectors capable of operating in the frequency range of from less than 1 GHz to 20 GHz.
2. Description of the Related Art
Conventionally, an electrical connector for use with printed circuit boards, for example, contained a plurality of solder pins for soldering to the printed circuit board. While this is still used in many applications, in the case of connectors for use in high-speed applications, particularly when it is desirable to have a connector with very close pin spacing to reduce its size, it has been found that soldering such a connector to a printed circuit board becomes very costly in that it is impossible to visually locate a short or ground between the connector and the printed circuit board. An expensive x-ray technique must often be used to inspect the connections since the solder pins are hidden under the connector. Furthermore, the increasing number of pins needed in such connectors make the soldering of such connectors to printed circuit boards more difficult, thereby reducing the production yield and accordingly increasing production costs.
Still furthermore, there are presently significant uses for compact electrical connectors, capable of operating in the frequency range of from less than 1 GHz to 20 GHz, and having large numbers of coaxial or twinaxial interconnections. Conventional electrical connectors are just not suitable for such applications.
In view of the problems noted above, attempts have been made to utilize solderless electrical connectors having some form of resilient contacts used to connect the electrical connector to the printed circuit board. For example, U.S. Pat. No. 6,386,890 to Bhatt et al. discloses a printed circuit board to module mounting and interconnecting structure and method. As illustrated in FIG. 3 thereof, a resilient conductor 52 to is used to connect a contact 34 to a contact 40. The conductor 52, as noted in column 5 thereof, may be a xe2x80x9cfuzzy buttonxe2x80x9d connector similar to those produced by Cinch Inc. Alternatively, the conductor 52 may be a plated elastomeric member, a precious metal plated wire or a stamped metal contact with precious metal plating. As further noted therein, it is preferable that the precious metal wire used for the conductor 52 have a random orientation to provide multiple contact points on the contacts 40 and 34, thereby increasing the reliability of the overall electrical connection by providing multiple hertzian contacts.
Unfortunately, the resilient contacts of Bhatt et al. have proven to be somewhat fragile in that they can be easily destroyed if they brush up against a hard surface. Furthermore, they are very expensive to produce and are very difficult to install in the electrical connector, thereby increasing production costs.
On the other hand, U.S. Pat. No. 6,341,962 to Sinclair discloses a solderless grid array connector that utilizes helical wound spring contacts to make solderless connections between an electrical connector and a printed circuit board. While such spring contacts are an improvement over the resilient contacts of Bhatt et al., they are very difficult to manufacture, particularly in the case of spring contacts having very small dimensions.
Furthermore, as noted above, electrical contacts are needed for use in an electrical connector to work with high frequency pulse or analog systems, that is, for use in a frequency range of from less than 1 GHz to at least 20 GHz .The electronic properties are critical. That is, the impedance of the electrical connector requires that the capacitive reactance be controlled, the inductive reactance be controlled and the resistance value be controlled. The overall performance depends on a specific impedance Zo, (i.e., such as 50 ohms, 75 ohms, etc.) needed to maintain a minimum insertion loss and minimum reflections of the charges launched in electronic circuits, over the bandwith in use. The dimensions of the connectors are critical to ensuring a minimum of electronic disturbance and to minimize any crosstalk between adjacent channels. These electrical connectors may be used for coaxial/twinaxial and transmission line systems on motherboard to daughterboard with high-speed processors. The simple spring arrangement of Sinclair does not work at these high frequencies.
In view of the above, it is an object of the present invention to provide a one-piece semi-rigid electrical contact with an integral compression spring for use in solderless high-speed electrical connectors.
These and other objects of the present invention may be achieved by providing an electrical contact comprising: a hollow tube having first and second end portions and a center portion; and a spring portion formed in a wall of said hollow tube.
The spring portion may be a helical spring portion and may be located in one of the first and second end portions or the center portion.
The helical spring portion may include turns wound in a first direction and turns wound in a second direction opposite that of the first direction.
At least one of said first and second end portions may have a diameter that is less than a diameter of said center portion and at least one of said first and second end portions may have a hemispherical shape or a closed end.
The hollow tube may be of a metal such as stainless steel or may be a hollow tube coated with an electrically conductive material such as copper, silver, or gold.
The contact may have a shoulder having a diameter that is greater than the diameter of at least one of said first and second end portions and said center portion of the tube.
The shoulder may be disposed between one of said first and second end portions and said center portion of the tube.
The shoulder may be disposed in one of said first and second end portions of the tube or in said center portion of the tube.
These and other objects of the present invention may also be achieved by providing a method of fabricating and electrical contact, the method comprising: forming a hollow tube having first and second end portions and a center portion; and forming a spring portion in a wall of the hollow tube.
The spring portion may be formed in the center portion of the hollow tube or in one of the first and second end portions of the hollow tube.
The spring portion may be formed as a helical spring portion and the spring portion may be formed with one of a cutting process, an etching process, and a laser cutting process.
The spring portion may have turns wound in a first direction and turns wound in a second direction opposite that of the first direction.
At least one of the first and second end portions may be formed with a diameter that is less than a diameter of the center portion.
At least one of the first and second end portions may be formed so as to have a hemispherical shape.
At least one of the first and second end portions may be formed so as to have a closed end.
The hollow tube may be formed of a metal such as stainless steel.
The hollow tube may be formed of a hollow tube coated with an electrically conductive material such as one of copper, silver, or gold.
A shoulder may be formed having a diameter that is greater than the diameter of at least one of the first and second end portions and the center portion of the tube.
The shoulder may be formed between one of the first and second end portions and the center portion of the tube or in one of the first and second end portions of the tube or in the center portion of the tube.